152120-54-2

24424-99-5

152120-61-1

152120-54-2

Step F-2: Synthesis of tert-butyl (tert-butoxycarbonyliminopyrazol-1-yl - methyl) carbamate [Compound (H) N-Boc-1H-pyrazole-1-carboxamidine (50 g) prepared in step BI was dissolved in tetrahydrofuran (100 ml) and slowly added to a suspension of 60% sodium hydride (9.99 g) in tetrahydrofuran (100 ml) over a period of 1 h. The temperature of the reaction was maintained at -5°C to 0°C. After 30 minutes of continuous stirring at this temperature, a solution of tetrahydrofuran (100 ml) of di-tert-butyl dicarbonate (57.1 g) was added dropwise, keeping the temperature constant. Subsequently tetrahydrofuran (250 ml) was added and the reaction mixture was heated and stirred at reflux for 2 hours. After completion of the reaction, it was cooled to room temperature, the reaction was quenched by the addition of acetic acid (20.4 ml) and concentrated under reduced pressure to about 150 ml. 5% aqueous sodium bicarbonate solution (500 ml) was added to the concentrate and extracted with ethyl acetate (500 ml). The organic layer was washed with water (150 ml) and concentrated under reduced pressure to about 75 ml. Hexane (200 ml) was added to the residue and inoculated with crystals, which were stirred under cooling in an ice bath for 40 min. The crystals were collected by filtration, washed with hexane (50 ml) and dried under reduced pressure to give N,N'-di-BOC-1H-1 -guanidinopyrazole (54.47 g, 73.8% yield). 1H NMR (CDCl3, 500MHz): δ 1.49 (9H, s), 1.55 (9H, s), 6.41 (1H, dd, J = 1.5, 2.7Hz), 7.62 (1H, dd, J = 0.7, 1.5Hz), 8.30 (1H, dd, J = 0.7, 2.7Hz), 8.93 (1H, brs). 13C NMR (CDCl3, 125MHz): δ 28.1, 28.2, 81.4, 83.4, 109.8, 129.0, 139.2, 142.8, 149.4, 157.4.